9:00 p.m.I sometimes wonder which is more creative: the screen names some of these men use or the excuses they give me once they’re caught. Tonight you’ll meet “Xclusivelyinit.” Even though the decoy tells this 30-year-old sales manager at a large electronics firm at least twice that she’s 13, he tries to tell me he thought she was 19. It turns out the man knows exactly what he’s walked into because he’s see our show before. He claims it’s all a big misunderstanding and that he’s “very professional”. But it’s when he’s interviewed by police, that the really creative excuses come out. First he says he was drunk and didn’t notice the girl’s age.

Then comes an excuse we’ve not heard before: the “I know all about ‘To Catch A Predator’ defense.” He suggests that because he knew all about the show, he wouldn’t have actually done anything with the girl. He even tells the detective to “talk to Chris” as if I could vouch for him. As you’ll see, the police are not buying it.

9:10 p.m.As you’ve probably noticed, here in Petaluma, we change the look of the area where we confront the men. In the past we’ve used a kitchen, basement or living room setting with a counter or bar. This time we are on the back patio. We have set up a bar, but there is also a hot tub. Will any of our visitors actually get in?

This next guy comes pretty close. Joseph Roisman is enlisted in the Navy, but he’s decided to take some of his time on leave to come to our house to meet someone who told him online that she’s 13. It takes him 5 hours to get here by bus and cab. He takes off his shirt off as he walks over to the hot tub. But before he finishes getting undressed, he goes looking for the decoy. Instead he finds me.

There is a really tense moment, not reflected on camera, where I can tell he’s going over his options. His stare is intense. He eventually sits down at the bar and talks. Roisman’s long journey is about to get even longer. He’s arrested and will eventually tell police he was looking for oral sex from the girl he thought was home alone.

9:30 p.m.You’re about to meet a man who so badly doesn’t want to appear on television, his lawyers actually went to court, trying to prevent us from using details of his chat, and video of his interrogation by police.

The court, however, ruled in our favor. He’s 48-year-old Maurice Wolin, a respected cancer doctor who lives near San Francisco. Dr. Wolin shows up after an online chat with a decoy posing as a 13-year old girl. He uses the screen name “Talldreamy_doc.” He lies to the girls and says he’s only 29. He asks the girl what bra size she wears, talks in graphic detail about giving and receiving oral sex and finally “Talldreamy_doc” says: “I’m horny for you.”

As you can imagine, I really wanted to talk to Dr. Wolin to find out why someone in his position would engage in such a conversation, much less show up for a meeting. Here’s why I never got the chance. After Dr. Wolin came into our backyard, our decoy asked him to pour her a frozen drink at the bar. It came out in a big chunk, knocking the glass over and spilling the drink all over the place. Dr. Wolin then walks over to the hot tub to grab a towel to clean up his mess. We think he spots a member of our crew and he runs off. Little does he know his mess is just beginning. As you’ll see, the Petaluma police are waiting and he’ll be talking to them.

9:50 p.m.It’s hard to watch our investigation tonight and not draw some comparisons between some of the prominent men we meet and former Congressman Mark Foley, who resigned a week ago today after it was learned that he sent inappropriate e-mails and instant messages to former Congressional pages. Of course there are differences between Foley and the men who surface in our stories: In our investigations the targets are younger, the conversations are more explicit, and the men actually travel meet a young teen in person.

Video: To Catch a Predator?
But there are similarities. Most notable, how prominent men can sometimes compartmentalize their lives in a way where they continue to perform professionally and be respected by family and friends, while still taking part in questionable, even illegal behavior online.

Former Rep. Mark Foley championed The Child Protection Act of 2006. In speeches, he railed against computer predators. And as you’re about to see, he even appeared on MSNBC’s Scarborough Country to compliment Dateline on our “To Catch A Predator” investigations. All of this took place after he’s alleged to have been sending these online messages.

The cartoon's balloon reads: "Hi I'm Chris Hansen from Dateline: To Catch A Predator." Obviously this is a reference to the
firestorm in Washington over the Mark Foley scandal. Foley, the recently resigned congressman, it appears, sent inappropriate e-mails and instant messages to young men who had once been in the Congressional page program.

While there are clearly differences between the allegations against Foley and those against some of the men who have surfaced in our Dateline investigations (our cases involve younger kids, much more graphic Internet conversations, and arrangements to meet the young teens for sex), it is again a reminder that when it comes to questionable behavior on the Internet, there is no segment of society that is exempt. The compulsions and addictions cross all classes and all professions.

As we wrap up our latest investigation, we see exactly that. Among the 29 men who show up at our hidden camera house in Petaluma, Calif. are military men, computer executives and a highly-regarded cancer doctor.

The doctor is 48 years old and has a big job at a research company near San Francisco. After an online chat with a decoy posing as a 13-year-old girl he arrives at our house for a date. Dr. Maurice Wolin, whose screen name is "Talldreamy_doc" asked online about the girl's bra size and oral sex. After a brief conversation with an actress posing as the young girl, he tries to pour himself a drink. He ends up spilling it and when he walks over to the hot tub to grab a towel, he appears to spot a member of our camera crew. He bolts before I can talk to him. But, as you'll see, he does talk to the police.

I think you'll find him and all the other men you'll meet in Petaluma among the most interesting we've seen so far.

9:10 p.m.
We try to know as much as we can about the men who visit our hidden camera houses before they walk in the door. Reading the chat log of the man’s conversation with a decoy posing at a young teen gives me a pretty good idea of who I’m dealing with, but it doesn’t always give me a sense of what criminal acts the man might have committed in the past. Such is the case with Norberto Avalos. Avalos comes into our backyard carrying gifts, food and a Web cam. He’s here to meet a 13-year-old girl but despite his sexually explicit online chat he tells me he really isn’t planning to have sex with her.

After Avalos and I finish our discussion he’s arrested by Petaluma Police. During his police interview he mentions that he’s been in trouble before, but he doesn’t get too specific. Now we have the court records and it turns out Avalos pleaded guilty back in 1998 to robbing a grocery store. According to court documents he had a .380 semi-automatic pistol with him. The court documents and investigators say Avalos and his brother bound and gagged two of the grocery store employees with duct tape during the stick-up. Avalos was sentenced to five years in prison.

9:20 p.m.
By now you may notice something different about the way our seventh investigation looks. As you know, we usually set up many of our hidden cameras in a kitchen or at a bar in the basement of a house. For this investigation we decided a fresh look was in order, so we decided to set up outside our house on the back patio. We had a bar with frozen lemonade and even a hot tub. It proves to be an inviting setting. More often than not tonight you’ll see the men walk right in, have chit-chat with our decoy, pour themselves a drink and wait as they think the decoy is going to change into something more comfortable for the hot tub. But as you have probably guessed by now, there will be no hot tub session for our visitors.

9:35 p.m.
It doesn’t happen very often, but we do have a bit of a mix-up here in Petaluma. A man walks up our driveway and into our back yard. He’s greeted by our decoy, who asks him what he wants to do. He says: “actions speak louder than words.” When I walk out to confront the man I quickly discover that I have the wrong chat log in my hands It’s not until the man tells me his screen name, “Hennesy1436” that we figure out just exactly who this guy is and someone can hand me the correct transcript. What causes the confusion? “Hennessy1436” is what Perverted-Justice calls a “fast mover.” It only took a few hours from his chat about sex with a young girl to his actual arrival at our house. He came over so quickly it threw off our schedule. As all this is going on, another visitor is waiting in front of the house in his truck. He ends up driving away, but is arrested down the street.

At its most basic level, some of what you’re watching tonight represents the crossing of the line between fantasy and reality. After talking to nearly 200 men who have chatted about sex online with a decoy posing as a young teen and who then travel to a house for a liaison, I am starting to see how that line gets blurry for some of these men. One of the men you’ll meet tonight tells me that he has had a 10-year addiction to chat rooms.

9:45 p.m.
In what will begin to resemble a therapy session, watch as Jeffery Couture admits to me that he’s developed fantasies that he calls “stupid.” He also says that he had collected pictures of teens he had chatted with online and tells police that he had considered getting rid of the pictures, but ultimately kept them in case he wanted to masturbate to them. He tells me that a while back he actually deleted his online identities in an effort to break his Internet addiction. It didn’t work.

And it’s not like this man doesn’t have anything else going on in his life. He’s a cabinet-maker with his own business. He says he’s got a girlfriend who is a doctor. But, recently he says he’s developed feelings of excitement about the idea of a young girl losing her innocence. At first he says he probably wouldn’t really have sex with a 13-year-old but then qualifies that -- indicating that it could happen if she looked as good as our decoy/actress. In the end he expresses relief that he can come clean and get some help.

As you’ll see, like the other 28 men who come to our hidden camera house Couture will also be arrested.

The next installment of the Petaluma investigation airs Dateline Friday, Oct. 6, 9 p.m. on NBC.

One of the first major stories I covered for NBC News was the kidnap and murder of Polly Klaas. Many of you will remember the disturbing nature of the crime. One evening in October of 1993, the 12-year-old girl was hosting a slumber party for a couple of girlfriends. In the middle of the night, someone came into her mother’s home through a window and snatched the child in her nightgown.

It’s the kind of crime you don’t see in a place like Petaluma, Calif.. It’s truly charming there. It has a quaint downtown and is surrounded by Sonoma Country’s renowned vineyards. Above all, it is perfectly safe. Except of course on the night that a sexual predator named Richard Allen Davis abducted Polly in front of her two friends. He later killed the girl and was ultimately convicted of first-degree murder and sentenced to the death penalty.

For as long as I live, I will never forget interviewing Polly’s father Mark Klaas in the hours after she was found. He had led the charge in the search for Polly and was doing the same in the search for her killer. It was the first time that I came close to even feeling what it would be like to lose a child.

The Polly Klaas case also had a profound impact on the Petaluma Police department. Its officers vowed never to let something like this happen again in their community. That’s part of the reason Detective Sergeant Matt Stapleton contacted the online watchdog group Perverted-Justice about doing an investigation there. Once again, we hired Perverted-Justice as a consultant to have its decoys go into chat rooms posing as young teens. In three days, 29 men came to the hidden camera house in an upscale Petaluma neighborhood after sexually explicit online conversations. All 29 were arrested as they left.

Again, the men came from all walks of life. There was a prominent doctor, computer executives -- and in this investigation, something I never seen before. While many of our visitors typically deny they would ever actually have sex with a young teen, you’ll meet one man who admits he has a problem. Watch as his interview with me turns into a virtual therapy session. It is truly telling.

Yesterday, I also appeared on Oprah as part of her special report on “What pedophiles don’t want you to know.”

We were surprised to find out that Oprah not only watches the ‘To Catch a Predator’ series — but also considers herself a big fan. Her show has educated the public about sexual molestation since its first season. In 1993, President Clinton signed the “Oprah Bill” into law, after the talk show host’s campaign for a national database of convicted child abusers. Today, she's advocating that the government standardize penalties for sexual predators, as state laws currently vary. She says she hopes to see something happen within the next five years.

During the taping, Oprah emphasized the Internet as one of the child predator’s most dangerous tools. We were glad to have been invited, but more importantly, that someone with a national and influential voice such as hers is continuing to educate the public about this problem.

Part 1 of the investigation in Petaluma airs Friday, Sept. 29, 9 p.m. on NBC.

Dateline wires the home of a volunteer, Jenny, from top to bottom with hidden cameras. Then she called repairmen to her house for a simple problem we created as a test with Jenny's pool. NBC's Chris Hansen reports.